1. Field of the Invention
The present invention relates to an antenna installed inside a mobile telecommunication terminal, for transmitting and receiving a wireless signal. More particularly, the present invention relates to a chip antenna installed inside a mobile telecommunication terminal, capable of processing a low band signal.
2. Description of the Related Art
Recently, a rising demand for wireless devices installed inside mobile telecommunication terminals has led to diversity in frequency bands used in an antenna of the terminals. Specifically, frequency bands currently used in the mobile telecommunication terminals include 800 MHz to 2 GHz (for mobile phones), 2.4 GHz to 5 GHz (for wireless LAN), RFID (113.56 MHz (for contactless RFID), 2.4 GHz (for Bluetooth), GPS 1.575 GHz (for GPS), 76 to 90 MHz (for FM radio), 470 to 770 MHz (for TV broadcasting) and other bands for ultra wideband (UWB), Zigbee, Digital Multimedia Broadcasting (DMB) and the like. The DMB band is classified into 2630 to 2655 MHz for satellite DMB and 180 to 210 MHz for terrestrial DMB.
Meanwhile, the mobile telecommunication terminals have been faced with demands for smaller size, lighter weight and various service functions as well. To meet such demands, the mobile telecommunication terminals tend to employ an antenna and other components which are more compact-sized and multi-functional. Furthermore, increasingly the mobile telecommunication terminals are internally equipped with the antenna. Therefore, to be installed inside the terminals, the antenna needs to occupy a very small space, while performing with satisfactory capabilities.
FIG. 1 is a structural view illustrating a conventional internal or built-in Planar Inverted F Antenna (PIFA).
The PIFA is an antenna designed for installation in a mobile telecommunication terminal. As shown in FIG. 1, the PIFA generally includes a planar radiator 2, a ground line 4 and a feeding line 5 connected to the radiator 2, and a ground plate 9. The radiator 2 is powered via the feeding line 5 and short-circuited to the ground plate 9 by the ground line 4 to achieve an impedance match. The PIFA needs to be designed by considering the length L of the radiator 2 and height H of the antenna in accordance with the width Wp of the ground line 4 and width W of the radiator 2.
The PIFA is characterized by directivity. That is, when current induced to the radiator 2 generates beams, a beam flux directed toward a ground surface is re-induced to attenuate another beam flux directed toward the human body, thereby improving SAR characteristics and enhancing intensity of the beam flux induced to the radiator 2. The PIFA operates as a rectangular micro-strip antenna, in which the length of a rectangular panel-shaped radiator is substantially halved, thereby realizing a low profile structure. Moreover, the PIFA is installed inside the terminal as an internal antenna so that the terminal can be designed with an aesthetic appearance and significantly withstand external impact.
The conventional internal antenna employs a high dielectric substrate so that it can be sized about 10 mm×10 mm at a frequency of 1 GHz or more. But in case where the antenna is required to process a frequency band of hundreds of MHz or less as in a mobile telecommunication terminal for terrestrial DMB, the antenna should be tens of centimeters in length (i.e., λ, λ/2 or λ/4, where λ is a wavelength of a radio-wave). For example, since the terrestrial DMB antenna has a center frequency of 200 MHz, a monopol antenna should be 39 cm in length (free space wavelength/4). Therefore, disadvantageously, the conventional internal antenna cannot process low band frequencies of e.g., terrestrial DMB. Also, the antenna should be sized 5 cm or less to be installed inside the mobile telecommunication terminal such as a portable phone. As a result, the antenna manufactured according to a conventional built-in technology is sized tens of cm or more, thus disadvantageously lacking applicability as an internal antenna.